In grinding art, it is frequently necessary for machines which grind bearing races to grind adjacent faces on a given bearing race. One such common bearing race which is ground is the inner race, or "cone", of a tapered roller bearing set. When grinding the cone, it is desirable to grind the track on which the rollers roll, and the "rib", which is the adjacent face or shoulder to the track, against which the rollers end thrust. When grinding the rib and track of a roller bearing, the method of grinding is termed "conjugate grinding".
To be further familiarized with the conjugate grind process, it should be noted that the geometry of a roller bearing cone generally has an included angle between the rib and track of less than 90.degree.. The exact angular relationship varies between manufacturers. It is further necessary when grinding the rib face, to establish a radius, or "break", at the outermost diameter of the rib face to eliminate what may be defined as a sharp edge and, again, the amount of break or radius at the outermost extremity of the rib face varies between manufacturers.
To shape the wheels necessary to perform the conjugate grinding operation, it is necessary to dress two adjacent faces on the grinding wheel; the longer face generally being referred to as the "track face", and the shorter, adjacent face is generally referred to as the "rib face". Further, the track face may often be dressed not entirely straight, but rather deviating from a straight line by some minute amount referred to as a "crown", so that any deformations in the track under load will be taken up by the crown amount against the roller and the rollers may bear on a straight face.
Many types of dressers are known in the prior art for dressing the adjacent faces on a conjugate grinding wheel, and by example of the more popular prior art devices, one uses only a single point diamond nib which is arranged to have its nib axis normal to the grinding wheel axis in such manner that as the nib is traversed with its slide in a direction generally parallel to the grinding wheel spindle, a tracing stylus will follow a stationary cam having the exact profile as is desired on the wheel faces, and the tracing stylus will impart motion to the nib to cause it to trace out the cam profile on the grinding wheel. One drawback to this type of operation is the fact that the diamond nib sees considerable wear, when changing directions: i.e. tracing the steep rib face and the radius, or "break" (which is a concave surface on the grinding wheel).
Further, as it is somewhat impractical to obtain generation of the radius required in the break, a special diamond nib is often used with the radius of the break formed on the diamond so that it may be merely plunged, or "gashed", into the break area. This involves using a costly diamond nib, which will not hold its form as it is progressively worn by the gashing action.
A second method of dressing the adjacent faces on a conjugate grinding wheel involves uses a truing device having two diamonds, each mounted to unique slides, which are parallel to the respective rib and track faces wherein each slide is actuated to dress a respective face. This results in a very complex truing mechanism having multiple slides and complex set up procedures.
A third, commonly used method of generating the faces on a conjugate grinding wheel involves using a rotry diamond wheel dresser which is plunged into the grinding wheel, wherein the diamond wheel dresser has an impression in its rotary surface which is the shape of the grinding wheel desired, and the diamond wheel is mounted with its axis parallel to the grinding wheel axis. This method of dressing the conjugate wheel faces is extremely expensive in that the diamond wheel must be tailor-made for each individual part, and any wear that is seen by the diamond wheel dresser may be ruinious to the accuracy of the wheel form desired. Further, since the diamond wheel is generally motorized, vibrational movements may be seen on the grinding wheel as chatter marks and while they may be immeasurable in some instances, their effect may be seen on the workpiece in the form of a chatter pattern.
Applicant has obviated the difficulties involved in the prior art devices by his invention of a unique wheel dressing unit, having a single slide, which utilizes a single point diamond nib to dress the track face on a grinding wheel, then employs an adjustably mounted rotary diamond dressing unit while continuing slide movement, to dress the rib face and corresponding break on the grinding wheel after the track face has been dressed.